Dynamo-electric machine.



V. A. FYNN.

DYNAMO ELECTRIC MACHINE.

APPLIUATION FILED JUNE 15,

Patentd 'Aug'. 25, 1 914 IN l/EN 70/? WITNESSES:

UNITED STATES PATENT OFFICE.

VALERE ALFRED FYNN, -OF ST. LOUIS, MISSOURI. ASSIGNOR T0 WAGNER ELECTRIC MANUFACTURING COMPANY, OF ST. LOUIS. MISSOURI, A CORPORATION OF MIS- SOURI.

DYNAMO-ELEC'IRIC MACHINE.

Specification 01' Letters Patent.

Patented Aug. 25, 1914.

Application filed June 15, 1912. Serial No. 703,779.

America, have inventeda certain new' and' useful Dynamo Electric Machine, of which the following is such a full, clear, and exact description as will enable any one skilled in the art to which it appertains to make and use the same, reference being bad to the accompanying drawings, forming part of this specification.

My invention relates to all such dynamo electric machinesv as carry windings embedded in slots or tunnels placed close to the air-gap. It is particularly applicable to single-phase and polyphase alternate current induction motors, to rotary converters without defined polar projection, and to direct current dynarn'os and motors having slotted armatures and field poles. It is known that; such machines, and particularly, those operating withalternating currents, produce most unwelcome humming or singing noises, which often militate against their use and are always disagreeable. Many'unsuccessful attempts have been made to find the cause for the-production of these noises and to provide remedies therefor.

I have discovered how the production of the noises mentioned may be avoided in machines of any size and any type, and my invention, therefore, consists in'providing means to this end. i a

I will describe my invention with reference to an alternate current induction motor of the usual type, comprising a stator without defined polar projections and a rotor revolving within said stator, both being provided with a'number of slots for the accommodation of the windings. To render such a structure noiseless, it is, of course, necessary to provide a stiff frame for the stator laminations and to suitably compress the stator and rotor-laminations. While these conditions must exist and have existed in prior machines, yet they, alone, do not render a machine noiseless. I have found that portion of the circuit, it is difiicult' 'to fulfil it for the air-gap. I have. however, found that this condition is absolutely fulfilled if the efi'ective width of the tooth crown of one member is made equal to the tooth pitch of the other member. For perfect results. it is necessary that the tooth crowns of both stator and, rotor be fully efi'ectirc. A machine, the air-gap cross-section of which is dimensioned as just described, will run silently, even if the air-gap is reduced to the smallest possible dimensions.

Referring to the drawings, Figure 1 illus trates a developed set of stator and rotor punchings suitable-for polyphase or singlephase alternate current motors and dimensioned according to this invention. while Fig. 2 indicates how the stator 0r rotor teeth should be shaped in order to make their crowns fully effective.

In Fig. 1, the stator punching is shown at the rotor punching at l. The former isv provided with a number of slots 2; the latter with a numherlof slotsfi. The opening of the stator slots is shown at 6, that of the rotor slots at 7, and it is seen that the crown width (1 of the stator tooth is equal to the crown width 6 of the rotor tooth plus a rotor slot opening 7 or, in other words, that the crown width rl of a stator tooth is equal to the rot r pitch RP. A careful examination of this figure will show that, in the case of on the magnitude of the stator slot opening- 6. The size of the rotor slot opening 7 is also immaterial, but those skilled in the art will understand that'it will be best, in all induction motors, to keep the size'of the slot openings 6 and 7 as small as leakage conditions Wlll allow.

In order to carry out my invention, it isnecessary to make the magnetically efiective crown width of the tooth of the preponderant member equal to the'tooth pitch of the other member. By prepoader'ant mer component of the revolving field is produced from,-the stator and the latter can, therefore, belooked upon as the preponderant memberg yIn-a rotary converter. it is the rotor .,,which 'is' the, preponderant member. I

, As previously indicated, anothercondition observedin producing a noiselessmachine'is'to so dimension the stator and rotor teethgas to make the; crown of each fully effective. Fig. 2 will help to illustrate my meaning.- The crown d of the tooth of a prep'onderant member shown in Fig. 2 is said to be fully effective when the flux threading the waist a of the toothcan so diyide beyond that waist as to produce a practically uniform density along the whole crown of said tooth or any portion or portions thereof which are, at any given instant, during the operation of the machine, opposite to a tooth or portions of teeth of the other member. This crown may be divided into-three portions: a central one a corresponding-in-size to the waist, and two side portions, or lips c. In order to make the \vholecro'wn (1 effective, the cross sections such asfb located in the path of the fluxes 8 and 10 threading the lips of the crown, should be such as not to raise the flux density' through any of those sections above that existing in the central portion a of the crown. This condition" will in most cases be jn'actically fulfilled if the distance 6 is made equal-to the distance a and no metal is' cut away fron i the tooth inside of the hypotenuse of the. right angle triangle formed by b andc. lhose skilled in the art will recognize that the design of fully effect ve tooth crowns should always takeintoconsideration the magnitude of the densities in the Waist. 5 i v Unsuccessful attempts have been made to produce noiselessmotors by designing them witha relatively large ail-gap and operating them at low densities; It 18 perfectly well .und rstood that a la rgc air-gap 1s detrimental in many respects andthat a low den sity is expensive. In building my improvcc dynamo electric machines, t IS not. neces sary to increase the air-gap beyond that necessitatedby mechanical. reasons and t e densities can be pushed as h' 1 as other of diti0ns will allow withou of producing a noisy machine be safely designed with an air-gap approxr mately dcterminedby the formula:

and that machines with rotors exceeding ten (10) inches in diameter can be designed with an air-gap approximately determined by the formula l Diam etr inmils J These air-gaps can be used in my improved dynamo electric machines without increasing thenoise in any way.

Having fully described my invention. what I claim as new and desire to secure by Letters Patent of the United States'isi 1. A dynamo electric machine having slotted members for the reception of windings, in which, in one member, the-portion of the width of the tooth crowns, over any part of which magnetic lines of force can distribute uniformly in the operation of the machine, is substantially equal to the tooth pitch of the other member.

A dynamo electric machine hating, slotted members for the reception of windings in which thewidth of the tooth crowns of one member is substantially equal to the tooth pitch. of the other member, the shape of the teeth of the first member being such that magnetic lines of force can distribute uniformly over the portions of the tooth crowns which are, at any given lnstant dur- .ing the operation of the machine, opposite to a tooth or portions of teeth of the other member. 1

A dynamo electric machine having laminated inducing and induced members. each provided with slots for the reception of windings. in which the width of the tooth crowns of the inducing member is substantially equal to the tooth pitch of the induced member, the shapeof the teeth of the inducing member being such that magnetic lines of force can distribute uniformly over the portions of the tooth at any given instant, during the operation of the machine, opposite to a tooth or portions or teeth of the induced member, said machine also having as small an air gap as mechanical conditions will permit.

In testimony whereof, I have hereunto set m hand and aflixed my seal in the presence two uhscribing witnesses.

VAL RE ALFRED FYNN. [L.s.]

ll-itnesses Y. A. ALEXANDER, EJE. HUFFMAN.

crowns which are. 

